Recently, with a spread of Internet, a purchase of goods on Internet has been recognized as a general transaction form, and an advertising on Internet has been established. The advertising on Internet includes an advertising system referred to as an affiliate advertising disclosed in Patent Document 1, for example. The affiliate advertising indicates an advertising system that an opener of a homepage or a blog posts a banner advertisement of a merchandise or a service which the opener intends to introduce at his/her webpage, and when a reader clicks the banner advertisement and visits a selling site of an advertise, thereby buying goods, for example, a result regard is paid by the advertiser to the site opener posting the banner advertisement.